In the diagnosis and treatment of breast cancer, it is often necessary to perform a biopsy to remove tissue samples from a suspicious mass. The suspicious mass is typically discovered during a preliminary examination involving visual examination, palpation, X-ray, magnetic resonance imaging (MRI), ultrasound imaging or other detection means.
When a suspicious mass is detected, a sample is taken by biopsy, and then tested to determine whether the mass is malignant or benign. This biopsy procedure can be performed by an open surgical technique, or through the use of a specialized biopsy instrument. To minimize surgical intrusion, a small specialized instrument such as a biopsy needle is inserted in the breast while the position of the needle is monitored using fluoroscopy, ultrasonic imaging, X-rays, MRI or other suitable imaging techniques.
Regardless of the method or instrument used to perform the biopsy, subsequent examination of the surgical site may be necessary, either in a follow up examination or for treatment of a cancerous lesion. Treatment often includes a mastectomy, lumpectomy, radiation therapy, or chemotherapy procedure that requires the surgeon or radiologist to direct surgical or radiation treatment to the precise location of the lesion. Because this treatment might extend over days or weeks after the biopsy procedure, and the original features of the tissue may have been removed or altered by the biopsy, it is desirable to insert at least one site marker into the surgical cavity to serve as a landmark for future identification of the location of the lesion.
Commonly assigned application U.S. patent application Ser. No. 11/242,334 discloses a variety of markers that use expandable filament portions to ‘hold’ a site marker in place within a biopsy cavity. That is, a site marker may include a bio-absorbable filament portion, such as a suture, with a marker attached thereto, where the marker is visible under multiple modalities and the suture will inhibit migration of the marker within the biopsy cavity. The filament portions of these structures typically define a site marker diameter that is greater than the outer diameter of a delivery cannula. In one embodiment, to insert a site marker within a biopsy site, the site marker is compressed (at least partially elastically deformed) to a dimension that will permit the site marker to be interposed within the delivery cannula. The site marker is interposed within an opening of the delivery cannula, and the site marker and cannula are sterilized. When in use, the cannula is inserted within a biopsy canal such that the opening of the delivery cannula is within the biopsy site, and the site marker is deployed into the biopsy site. Once deployed, the site marker will expand as the filament portions exit the cannula in reaction to the elastic deformation. The site marker will expand until the elastic deformation is eliminated or portions of the site marker interfere with the inside portions of the biopsy cavity.
The site marker and cannula must be sterile in order to be placed into a biopsy cavity. However, the elastically deformed filament portions, or other materials, plastically deform within the cannula due to the heat of sterilization (essentially converting some of the elastic deformation to plastic deformation). Therefore, the filament portions may not properly expand upon exiting the delivery cannula. Lack of sufficient expansion may permit migration within the biopsy cavity.
Accordingly, there is a need for site markers and delivery systems that are compatible with sterilization and packaging techniques.